1. Field of the Invention
This invention relates to apparatus for contacting a liquid, in a tank containing a body of same, with a gas from a gas space overlying the body of liquid.
2. Description of the Prior Art
In the field of gas-liquid contacting, and in particular activated sludge sewage treatment, three general types of aeration devices have been widely employed in practice: submerged porous diffusers, submerged turbines, and surface aerators.
Although submerged diffusers represent the simplest apparatus design, surface aerators have become the most widely used of the basic sewage aeration devices. High efficiency and minimal operational complexity are probably the major reasons behind the popularity of the surface aerator. It is well known, however, that the highest efficiencies are achieved with surface aerators at low rotational speeds, typically below 100 rpm. Since commercially available drive motors typically operate at high rotational speeds, efficient operation of a surface aerator requires the use of a large, heavy and complex gear reduction unit. The need for this gear reduction unit increases both the capital and operating cost of the overall aeration system.
Accordingly, it is an object of the present invention to provide an aeration device that possesses the simplicity of the surface aerator while exhibiting optimum performance characteristics at higher rotational speeds than are employed with surface aerators.
Other objects and advantages of the present invention will be apparent from the ensuing disclosure and appended claims.